Design Decisions: Choosing the Right Silicone Adhesive

Silicone adhesives have several important performance characteristics that distinguish them from other adhesive families. Overall, users can rely on silicones to create bonds that withstand high temperatures (as high as 600F for certain grades), stay flexible even after curing, and resist both chemicals and water. Silicone systems also feature impressive electrical properties and may be formulated to be insulative with high dielectric strength or, conversely, electrically conductive. Although some one-part silicones release corrosive entities such as acetic acid, special noncorrosive formulas are available and are well suited for electronics applications. For example, these specialized silicone adhesives are frequently used as conformal coatings for electronic circuit boards and for sealing cables and sensors in appliances and electronics.

Within the broad classification of silicone adhesives are specific product types that feature unique advantages. To make the best selection, it is wise to discuss application details with your adhesives supplier at the earliest opportunity.

One-part specialty adhesives
One-part silicone adhesives, sealants, and coatings are often used in optical and electrical applications for assembly and repair tasks. Within the one-component family of silicone systems are a wide variety of specialized products offering various features. All products are environmentally friendly and free of both solvents and diluents, are easy to apply, and provide superior flexibility along with high-temperature resistance. They are well suited for strong adhesion to glass, plastics, metals, rubbers, and other substrates. Among their chief benefits is ease of use: They cure at ambient temperatures without the need for additional curing agents and are available with user-friendly applicators.

Beyond these common features, specialized product grades offer optical transparency and resistance to vibration, shock, enhanced heat, and corrosion. Other one-part silicones are designed to withstand extreme humidity, provide electrical insulation, or conduct heat and electricity, among other application-specific qualities. Certain grades are certified to meet military standards (MIL Specs) and UL requirements for flame retardance.

To understand just how versatile one-part silicone systems can be, it's helpful to take a closer look at some individual products. Consider the widely specified MasterSil 705TC, an easy-to-use, thermally conductive, electrically isolating, high-performance silicone employed in bonding, sealing, and coating applications. It comes as an off-white, noncorrosive paste and readily cures at ambient temperatures using only atmospheric moisture. It is especially well suited for thermally conductive applications where the need to rework the assembly may be important.

Nice detailed article, Robert. I would imagine part of the choice in silicone adhesives has to do with the manufacturing environment. How fast adhesives can be applied in the process and other concerns.

sensor pro, on the second page of my article on structural adhesives and fasteners

http://www.designnews.com/document.asp?doc_id=237011&page_number=2

Heather Doughty from Fabrico mentions structural adhesives that are stable at up to 225F, although without naming specific brands. I suspect Fabrico will know if what you want exists, and which suppliers provide it.

Practically all electronic devices today contain metals that may
be coming from conflict-ravaged African countries. And political pressures will increasingly influence how these minerals are sourced and used in products.

Design for manufacturing (DFM) in mold production means that mold designers evaluate the manufacturability of their molds in the early stage of mold development by collecting all relevant information and applying it to their designs. They also have to consider many other factors, including flow balance, structural stress, and assembly tolerance, in order to ensure successful molding production.

Some adhesives provide strong structural bonds but take hours to fixture and attain handling strength. The technologies that offer the fastest cure do not bear loads or withstand stresses. A new class of adhesives aims to make both stick.

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